Pump for delivering small discrete quantities of liquid



PUMP FOR DELIVERING SMALL DISCRETE QUANTITIES OF LIQUID Filed Dec. 27, 1952 I 38 i FIG. I 5 5 a III.

INVENTOR:

JOHAHNES 'T.M. SCHLAMANN RIS ATTORNEY United States Patent PUMP FOR DELIVERING SMALL DISCRETE QUANTITIES OF LIQUID Johannes T. M. Schlamann, Delft, Netherlands, assignor to Shell Development Company, Emeryville, Calif., a corporation of Delaware Application December 27, 1952, Serial No. 328,170

Claims priority, application Netherlands December 20, 1951 7 Claims. c1. 103-31 This invention relates to pumps having reciprocating plungcrs performing the dual function of closing off the pump chamber and driving the liquid for delivering successive small, controlled quantities of liquid. By the expression small quantities is meant such an order of magnitude as may occur, for example, in the following uses for which the pump is particularly adapted: in pharmacy, for filling ampoules; in agriculture, for injecting or discharging biocides; in reciprocating internal combustion engines, for supplying fuel to the cylniders in timed relation to the cycle of operation. Such quantities are typically between about 0.005 and 1.0 cubic centimeter per stroke of the plunger, but the invention is not limited to pumps of sizes to deliver such quantities.

There are many uses for pumps that deliver measured discrete quantities of liquid and are inexpensive and simple and are nevertheless adapted for high speed operation, such as one stroke for each power stroke of reciprocating internal combustion engines. Prior pumps have had the drawback that they were either complex and expensive or were not well adapted for operation at such frequencies of repetition.

The main object of this invention is, therefore, to provide a pump of the character described that is of simple construction, economical to produce and has only few moving parts. Ancillary objects are to provide a pump that is adapted to operate at high speeds or frequencies of repetition, of the magnitude indicated above, and wherein the quantity of liquid delivered per stroke of the plunger can be varied. The pumps described herein as specific examples are particularly adapted for use .as a fuel injection pump for an internal combustion engine with fuel injection at a relatively low pressure point of the cycle, for example such as that described in copending application Serial No. 282,176, filed April 14, 1952, of which this is a continuation-in-part; and .as a biooide pump, e. g., to be mounted on an agricultural vehicle to deliver successive charges of nemacide to a dispensing nozzle for treating soil at a succession of spaced points.

In summary, the pump according to the instant invention has a chambered pump casing defining a supply chamber to which liquid is admitted under low or moderate pressure and within which is an axially reciprocating plunger or piston having an end abutment face, the easing wall opposite the end of the plunger consisting at least in part of a wall section of highly elastic material adapted to be deformed by the plunger, said section having a hole piercing the said section and in alignment with the plunger axis to be closed by the end of the plunger upon engagement thereby, said hole forming an expansible pump chamber and being in communication with a discharge duct having a pressure-responsive discharge valve, which may be situated either in close proximity to the pump chamber or at some distance removed therefrom. The plunger is, in its outer position, in spaced relation to the deformable elastic wall section, permittting liquid from the supply chamber to enter said hole or pump chamber. On the inward stroke the plunger first closes the hole,

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thereby trapping liquid therein and completion of the inward stroke deforms the wall section, thereby reducing the volume of the pump chamber and forcing liquid out through the discharge valve. On the return stroke of the plunger the hole is uncovered, permitting a fresh charge of liquid .to enter the hole.

According to a further feature of the invention, particularly suitable when the pump is to supply liquid in fairly precise amounts at high or variable delivery rates, the pump is provided with (l) a continuously operating auxiliary pump or other source of moderate pressure for supplying the liquid into the supply chamber of the pump casing and (2) a discharge line from the supply chamber controlled by a pressure-limiting overflow valve set to pass liquid, e. g., for return to a reservoir, at a suitable pressure was to prevent the opening of the pressure-responsive discharge valve of the pump chamber merely by the pressure of the liquid in the supply chamber.

The quantity of liquid delivered at each stroke of the pump can be varied by varying the effective stroke of the pump, i. e., the part of the stroke during which the elastic wall is deformed. This can be effected in any desired manner, e. g., by altering the operation of the cam or other device that drives the plunger or by keeping the limits of travel of the plunger fixed and moving the pump casing in the direction of the axis of the reciprocation of the plunger.

The plunger of such a pump can be driven in a simple manner by means of a cam or similar device, which displaces the plunger into the chamber against the force of a spring, the spring serving to move the plunger outwardly against the .carn.

The sealing between the plunger and pump casing is effected by any suitable means, preferably a diaphragm within the pump casing which shuts off the annular space between the inner wall of the pump casing and the plunger to define the said supply chamber between itself and the deformable wall.

The invention will be described in greater detail with reference to the accompanying drawing forming a part of this specification .and illustrating three preferred embodiments of the invention, wherein:

Figure l vis a vertical sectional view of a pump according to the invention intended for use as a fuel injection pump.

Figure 2 is a vertical sectional view of a modified construction of the pump, particularly intended for agricultural use, including means for adjusting the effective stroke; and

Figure 3 is a fragmentary vertical sectional view of a further modified construction employing a spacer on the elastic wall section.

Referring to the drawings in detail, in Figure 1 the pump has a chambered casing formed of mating upper and lower sections 25 and 25a, respectively, shaped to provide an integral upstanding cylindrical tubular guide or sleeve 26 and an integral, depending, externally threaded discharge tube 27, the sections being secured together by suitable means, not shown. A plunger 28 is vertically slidablc within the bore of the guide tube 26 and has an enlarged head 29 which is advantageously conical, as shown to provide a downwardly directed end face of extended area. The upper end of the plunger is fitted with a cap or cam follower 30, which is kept permanently pressed against a cam 31 that is rotatable with a drive shaft, not shown, by a helical compression spring 32. The upper part of the plunger is sealed off from the lower part by a flexible diaphragm 33 which is clamped between the sections 25 and 25a and is sealed to the plunger by collars 34.

A valve housing 35 is threaded to the tube 27 and has a discharge tube or duct 36 which may be externally threaded as shown to receive a further pipe, dispensing or atomizing nozzle, etc., as desired. A spring-loaded pressure-responsive discharge valve 37 has an integral, fluted stem vertically reciprocable within the bore of the tube 27, the vertical flutes permitting the downward flow of liquid. It is urged upwardly by a helical compression spring 38 to seat against the bottom of the tube 27. The valve 37 thus serves to close the bottom of the tube 27 against flow of liquid either upward or downward except when the pressure within the tube rises to a predetermined value sufiicient to unseat the valve to permit downflow.

The pump casing defines a supply chamber 39a beneath the diaphragm 33, said supply chamber being in communication with the bore 39 of the tube 27. Liquid under low or moderate pressure is admitted to the supply chamber through a supply duct 49 from any suitable source to maintain within the supply chamber a pressure insuflicient to unseat the discharge valve 37. According to a preferred arrangement, the fuel pressure in the supply chamber is controlled by venting liquid therefrom as required through an overflow discharge conduit 41 having a pressure relief overflow valve 42 loaded by a compression spring 43 and connected to a discharge duct 44 by which excess liquid is returned to a reservoir. The liquid may be supplied by an auxiliary pump, such as a gear pump 45 that takes suction from a supply line 46 and may be operated continuously to pump liquid at a rate slightly greater than the delivery rate of the main pump. It is evident that the gear pump, although inherently capable of supplying liquid at high pressures, cannot unseat the valve 37.

The lower wall of the supply chamber 39a has a wall section of highly elastic material. In the embodiment of Figure 1 this wall section is a sheet of elastic material 47 of appreciable thickness. The exact composition of this material is selected in accordance with the properties of the liquid to be pumped so as not to be deleteriously afliected thereby; when gasoline and the like is handled it is preferred to use synthetic rubber, such as materials known by the trade name Neoprene or Acril. The sheet 47 has 'a hole or open-ended chamber 48 which is in communication at the lower, outer end thereof with the bore 39 and in alignment with the axis of the plunger 28; this chamber smaller than the head 29 so as to be closed thereby and may be conically countersunk from the top as shown to conform to the shape of the head. The said open-ended chamber forms an expansible pump chamber and that is in free communication at the upper, inner end thereof with the supply chamber 39a when the plunger is in the raised position shown in the drawing.

The pump operates as follows: By means of the auxiliary pump 45 the supply chamber 3% is kept continuously filled with liquid and the pump chamber 48 is likewise filled while the plunger uncovers it. The construction is such that, as a result of the excess pressure set up by the action of the auxiliary pump, the overflow valve 42 is opened sooner than the non-return discharge valve 37. The plunger 28 is periodically depressed by the cam 31, once each time the lobe 57 thereof engages the cap 30. After the plunger has completed a part of its inward stroke the head 29 thereof engages the elastic Wall 47 and closes the inner end of the pump chamber 48; this isolates the pump chamber from the supply chamber 39a. During the subsequent part of the inward stroke of the plunger the latter elastically compresses and deforms the wall 47; this reduces the volume of the pump chamber. The liquid trapped in the latter is thereby subjected to increased pressure which opens the valve 37 and results in the flow of a definite quantity of dependent of the length of that part of the stroke of the of the cam, or as described below for Figure 2.

As soon as the plunger 28, during its return stroke, no longer blocks the entrance to the pump chamber 48 in the elastic wall the liquid therein is supplemented by liquid from the supply chamber 39a; the valve 37 is already closed by this time since the spring 38 is sufliciently stiff to overcome the greatest pressure permitted in the supply chamber by the overflow valve 42. It is evident that the stiffness of the spring 38 also'has a certain amount of influence on the quantity of liquid delivered per stroke.

In the modified arrangement of the pump shown in Figure 2, wherein like reference numbers denote like parts, the pump casing, comprising sections 25b and 250 that are suitably fixed to each other, is modified in certain respects, including the omission of the auxiliary pump, the overflow duct and the diaphragm; instead, liquid is supplied under a low pressure by a duct 55, e. g., by gravity from an elevated reservoir, not shown, and the plunger 28 is sealed to the casing by an O-ring 24. A coupling member 52 is attached to the bottom of the casing section 250 and metallic tubing 53 connects the bore 39 to a dispensing or applicator nozzle comprising a pair of rubber lips 54 pressed together by resilient fingers 55 to close the nozzle except when the liquid pressure in the pump chamber and tube rises to above a predetermined value. The nozzle thereby constitutes the discharge valve. The pump casing is mounted on a support member 56 by studs 58 that are fixed to the casing and are vertically slidable on the support. Springs 59 and nuts 69 urge the pump casing downwardly With respect to the support A positioning ring 61 having an adjusting handle 62, rests on the support 56 and is in threaded engagement with the lower pump casing 25c. It is evident that movement of the lever 62 to rotate the positioning ring moves the pump casing and the elastic wall 47 thereof vertically with respect to the cam 31, the axis of which is fixed in relation to the support 56, whereby the effective length of the stroke can be varied to vary the quantity of liquid delivered per stroke. The lever can be secured in any adjusted position by means of a locking nut 63.

The device according to Figure 2 is particularly adapted for injecting controlled quantities of agricultural biocides. Thus, the support 56 may be a part of an agricultural vehicle for planting seeds wherein it is desired to inject or disperse a small quantity of a nemacide toward the ground between seeds, the cam 31 being operated in synchronism with the seed dispensing mechanism was to avoid wetting the seed with the nemacide.

In the modified embodiment of the pump shown in Figure 3, wherein like reference numbers indicate parts corresponding to those described for Figure l, the elastic wall section 47a is faced with a metal spacer 49 having a dependent sleeve 50 formed integrally therewith and vertically slidable within the bore 39 of. the tube 27.

A stop ring 51, secured to the side wall of the casing section 25a, limits the upward travel of the spacer. The upper edge of the sleeve is bevelled, as shown, to conform to the shape of the plunger 29. This spacer separates the Wall section from the plunger head and provides seat therefor, whereby the wall section is protected against deterioration by repeated impact of the plunger head.

The operation of the pump of Figure 3 is identical in principle with that previously described for Figure l but the plunger head 29 does not physically engage the elastic wall section 47a; instead, it seats on the upper, beveled edge of the sleeve to isolate the discharge pump chamber beneath the plunger head from the supply chamber 39a initially and, upon continued downward movement, to move the spacer downwards, thereby elastically compressing the wall section 47a and reducing the volume of the pump chamber. When the plunger is retracted the wall section 47a restores the spacer 49 to the position shown in the drawing. The stop ring 51 prevents the spacer from following plunger during the continued upward movement of the latter. The advantage of this construction is that, as regards the quality of the elastic wall section, the possibility of this section being attacked by the liquid to be pumped need not be considered or becomes of lesser importance, as the upper face and hole thereof do not come into contact with the liquid. Further, wear of the elastic section by contact with the plunger is obviated.

As far as construction is concerned, the design of the pump described herein is not restricted to the embodiments represented in the drawings. Thus, for example, the shapes of the valves or of the stamp-shaped plunger can differ from those given, provided they conform to the principles of the pump mentioned.

The pump is suitable for pressures up to about 20 atmospheres, and requires little maintenance and care during use.

If the pump is applied to an engine for installation in vehicles, e. g., to inject gasoline to the engine cylinder, the engine can be relied upon to run for 20,000 to 30,000 miles before replacement of the elastic wall becomes necessary. This elastic wall has proved capable of withstanding deformation up to 50,000,000 times before damage occurs.

The pump is also suitable for many other applications, e. g., for filling small reservoirs, arnpoules, and the like with various liquids such as pharmaceuticals or for admixing a small quantity of a liquid additive to a basic liquid, as may be required in the chemical industry or for adding anti-knock fluid to fuel in engines.

1 claim as my invention:

1. A pump for delivering small, discrete quantities of liquid comprising: a chambered pump casing defining a supply chamber and having a wall section of highly elastic material with appreciable thickness, said well section having an open-ended chamber extending therethrough forming an expansible pump chamber communicating at the inner end with said supply chamber; a discharge duct connected to the other end of said pump chamber; a discharge valve in said discharge duct; means for supplying liquid to said supply chamber; and a reciprocable plunger having an end abutment face in said supply chamber mounted for movement toward said pump chamber and shaped to close the said inner end of the pump chamber and to compress said wall section elastically upon engagement therewith and thereby to reduce the volume of the said pump chamber.

2. A pump according to claim 1 wherein said elastic wall section has the elastic material thereof exposed directly to the interior of the supply chamber whereby the abutment face of the plunger contacts the said elastic material directly to compress the wall section.

3. A pump according to claim 1 wherein said elastic wall section is covered by a metal spacer forming a facing for the wall directed toward the supply chamber and having a sleeve projecting into said open-ended chamber, whereby said abutment face of the plunger engages said spacer for moving said spacer and sleeve to compress the elastic wall section.

4. In combination with the pump according to claim 1, drive means external of said supply chamber for reciprocating said plunger to a constant inner position, support means for the pump casing, and means for adjusting the position of the pump casing in the direction of reciprocation of the plunger, whereby the extent to which the plunger compresses the elastic wall and, thereby, the quantity of liquid delivered at each stroke of the plunger can be adjusted.

5. A pump according to claim 1 wherein said plunger extends out of the casing through an opening in the casing opposite to said elastic wall section, said pump having means for reciprocating said plunger including a cam-like mechanism in engagement with an outer part of the plunger urging the plunger toward the elastic wall section and a compression spring acting on the plunger urging it against the said mechanism.

6. A pump according to claim 1 wherein said plunger extends out of the supply chamber, said casing having a flexible diaphragm spanning the space between the walls of the supply chamber and the plunger and sealed to said walls and to said plunger.

7. A pump according to claim 1 wherein: the said discharge valve of the discharge duct is a pressure-responsive valve adapted to open only upon a rise in pressure in the pump chamber above a predetermined value; said means for supplying liquid to the supply chamber includes an auxiliary pump adapted to supply said liquid continuously under moderate pressure and having the discharge thereof connected to said supply chamber; and the pump is provided with an overflow discharge conduit communicating with the supply chamber and having a pressure-limiting overflow valve adapted to discharge liquid at a pressure lower than the said predetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS 2,038,090 Smith Apr. 21, 1936 2,415,571 Yuza Feb. 11, 1947 2,494,344 Mannheim Jan. 10, 1950 FOREIGN PATENTS 570,110 France Apr. 24, 1924 

1. A PUMP FOR DELIVERING SMALL QUANTITIES OF LIQUID COMPRISING: A CHAMBERED PUMP CASING DEFINING A SUPPLY CHAMBER AND HAVING A WALL SECTION OF HIGHLY ELASTIC MATERIAL WITH APPRECIABLE THICKNESS, SAID WALL SECTION HAVING AN OPEN-ENDED CHAMBER EXTENDING THERETHROUGH FORMING AN EXPANSIBLE PUMP CHAMBER COMMUNICATING AT THE INNER END WITH SAID SUPPLY CHAMBER; A DISCHARGE DUCT CONNECTED TO THE OTHER END OF SAID PUMP CHAMBER; A DISCHARGE VALVE IN SAID DISCHARGE DUCT: MEANS FOR SUPPLYING LIQUID TO SAID SUPPLY CHAMBER; AND A RECIPROCABLE PLUNGER HAVING AN END ABUTMENT FACE IN SAID SUPPLY CHAMBER MOUNTED FOR MOVEMENT TOWARD SAID PUMP CHAMBER AND SHAPED TO CLOSE THE SAID INNER END OF SAID PUMP CHAMBER AND TO COMPRESS SAID WALL SECTION ELASTICALLY UPON ENGAGEMENT THEREWITH AND THEREBY TTO REDUCE THE VOLUME OF THE SAID PUMP CHAMBER. 